This would be a reusable lander: The lander consists of a stripped-down version of Dragon's pressure hull permanently mounted into a structural frame at the bottom. Set the lower part of the cabin into a frame that contains 2 banks of hypergolic propellant tanks (upper and lower banks) and lander legs. The lower bank of tanks provide propellant to Dragon's SDs for the descent and are dropped onto the lunar surface before ascent. The upper bank of tanks provide propellant to Dragon's SDs for the ascent burn and are dropped off in LLO after reaching it. Crew transfers back to Orion and goes home. Returning Orion for next mission brings fresh (full) tanks that are mated to the lander frame that was left in the stable LLO. Crew descends to lunar surface in this reusable lander and executes next mission. Will have to decide how many missions the lander is good for before it needs to be replaced.

Everything happens in a vacuum so we don't need clean lines. This will be ugly as hell but should work beautifully.

There would be no separate ascent or descent stage. Dragon IS the lander with a structural frame to contain and connect propellant tanks to her SDs. The frame is permanent. Only the emptied tanks are discarded. There would be no propellant "transfer" as brand new completely full tanks, brought along by the returning Orion would simply be connected to the plumbing.

This would be a reusable lander: The lander consists of a stripped-down version of Dragon's pressure hull permanently mounted into a structural frame at the bottom. Set the lower part of the cabin into a frame that contains 2 banks of hypergolic propellant tanks (upper and lower banks) and lander legs. The lower bank of tanks provide propellant to Dragon's SDs for the descent and are dropped onto the lunar surface before ascent. The upper bank of tanks provide propellant to Dragon's SDs for the ascent burn and are dropped off in LLO after reaching it. Crew transfers back to Orion and goes home. Returning Orion for next mission brings fresh (full) tanks that are mated to the lander frame that was left in the stable LLO. Crew descends to lunar surface in this reusable lander and executes next mission. Will have to decide how many missions the lander is good for before it needs to be replaced.

Everything happens in a vacuum so we don't need clean lines. This will be ugly as hell but should work beautifully.

There would be no separate ascent or descent stage. Dragon IS the lander with a structural frame to contain and connect propellant tanks to her SDs. The frame is permanent. Only the emptied tanks are discarded. There would be no propellant "transfer" as brand new completely full tanks, brought along by the returning Orion would simply be connected to the plumbing.

So this is a vertical lander then? Also it would need to be launched in a faring as you already know...

Threw this sketch together a couple of minutes ago to show what I mean.It's really, really rough but I hope you get the idea.Fold the legs in - Apollo LM style for transport.FH should be able to drop this into LLO as long as it doesn't carry any propellant tanks with it.Just the dry mass lander.

The frame should be sized to fit inside the Trunk, opened at the top of course.The cabin would need a fairing to cover it for launch.

Threw this sketch together a couple of minutes ago to show what I mean.It's really, really rough but I hope you get the idea.FH should be able to drop this into LLO as long as it doesn't carry any propellant tanks with it.Just the dry mass lander.

I always like reusable! You are going to need to replace the drop tanks after ever mission then?

Threw this sketch together a couple of minutes ago to show what I mean.It's really, really rough but I hope you get the idea.FH should be able to drop this into LLO as long as it doesn't carry any propellant tanks with it.Just the dry mass lander.

I always like reusable! You are going to need to replace the drop tanks after ever mission then?

Yes. Every arriving Orion crew would bring new (full) tanks that they would connect to the lander, plus whatever else they needed for the surface mission. No messy propellant transfer. Just connect the tanks and go.

It's not pretty but it meets SpaceGhost's requirements in the OpEd on page 1 (I think). Now to do the math.

Threw this sketch together a couple of minutes ago to show what I mean.It's really, really rough but I hope you get the idea.FH should be able to drop this into LLO as long as it doesn't carry any propellant tanks with it.Just the dry mass lander.

I always like reusable! You are going to need to replace the drop tanks after ever mission then?

Yes. Every arriving Orion crew would bring new (full) tanks that they would connect to the lander, plus whatever else they needed for the surface mission. No messy propellant transfer. Just connect the tanks and go.

Threw this sketch together a couple of minutes ago to show what I mean.It's really, really rough but I hope you get the idea.FH should be able to drop this into LLO as long as it doesn't carry any propellant tanks with it.Just the dry mass lander.

I always like reusable! You are going to need to replace the drop tanks after ever mission then?

Yes. Every arriving Orion crew would bring new (full) tanks that they would connect to the lander, plus whatever else they needed for the surface mission. No messy propellant transfer. Just connect the tanks and go.

Perhaps toroidal tanks could be mated without having to go EVA...

That works, but not 360 degrees all around. Hemispherical; 1/2 each of the required hypergol. One pair for the upper bank and 1 pair for the lower bank. Remember there's nothing in the middle. We can completely fill the space under the lander.

On second thought go all around with a single tank with a common bulkhead separating the 2 propellants. One for the upper load and one for the lower load.

Threw this sketch together a couple of minutes ago to show what I mean.It's really, really rough but I hope you get the idea.FH should be able to drop this into LLO as long as it doesn't carry any propellant tanks with it.Just the dry mass lander.

I always like reusable! You are going to need to replace the drop tanks after ever mission then?

Yes. Every arriving Orion crew would bring new (full) tanks that they would connect to the lander, plus whatever else they needed for the surface mission. No messy propellant transfer. Just connect the tanks and go.

Perhaps toroidal tanks could be mated without having to go EVA...

That works, but not 360 degrees all around. Hemispherical; 1/2 each of the required hypergol. One pair for the upper bank and 1 pair for the lower bank. Remember there's nothing in the middle. We can completely fill the space under the lander.

On second thought go all around with a single tank with a common bulkhead separating the 2 propellants. One for the upper load and one for the lower load.

Dragon seats could be on a semi-circular track for take-off and landing and the display on a pivot if one wishes eyeballs out the window...

Apollo LM didn't have seats at all. The astronauts stood up. If mass is an issue they could do the same. Interior would not resemble the crew dragon very much. Very different mission profile, very different ergonomics.

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Dragon seats could be on a semi-circular track for take-off and landing and the display on a pivot if one wishes eyeballs out the window...

Apollo LM didn't have seats at all. The astronauts stood up. If mass is an issue they could do the same. Interior would not resemble the crew dragon very much. Very different mission profile, very different ergonomics.

I'd like to see how the Dragon 2 hatch could be adapted to work with a porch/ladder for EVA egress. And would it be a good idea to have the suits able to join with the hatch or hull as external 'suit locks' after the first EVA? I've become a bit of a fan of suit locks - keeps the dust out of the Lander interior, which was always strongly advocated by John Young and Gene Cernan in particular.

I may be pushing the boundaries of Dragon or Starliner-derived lander here - so, SpaceGhost, if you feel I have, let me know and I'll delete my post.

It's a fine post. On topic and relevant. I'll attempt to give you feedback.

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Operating premise; keep costs down, including R&D. Use existing tech (Dragon2, in this case) as much as possible. That means, in part, keep it as simple as possible. It also means avoiding unneeded mass. It would require lunar orbit rendezvous like Apollo.

Correct. And the existing tech also includes associated mission systems. Since docking is standardized, other vehicles that may be used like Orion have systems as well, but outside of such standardized interfaces, you don't "mix and match".

You do LOR because of the limitations of the combined systems. Each has a means to arrive on LLO. Adding complexity to share the ride slows things down. And you can use the excess performance margin for extended capabilities later. But it introduces risk, contingencies, and variables. Likely you want the CC derived lander on LLO ahead of crew launch, and thus it must last significantly longer.

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First, Dragon 2 needs a propulsion service module to enter and leave lunar orbit. (please bear with me here, as this is directly relevant to the lander design).

Wouldn't call it a SM. Dragon has an integral SM.

Would call it a jettison-able propulsion assist pallet (JPAP). Use the Dragon's trunk/radiator/other systems to keep PMF low, might construct CF tanks with integral thrust structure and membranes to get below F9US PMF.

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Essentially, a cylinder, slightly smaller in diameter than the F9 (to fit within the Dragon trunk), containing Superdracos (2, for redundancy) and fuel. Theoretically, you should be able to make this with about the same mass ratio as the upper stage. It'll be a short cylinder, mounted behind the trunk, size dictated by needed delta/v and thus tankage capacity.

Not how you do it.

You calculate your mission's needs, including contingencies venting etc, the length of engines/nozzles/gimbal freedom/recontact margin/jettison compliance/other. From these you get the overall tanks/pallet dimensions, size the trunk from that. Not the other way round. Oh, and I forgot, you need to add mission growth margin.

Then you can call it short, medium or long.

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Needed Delta/v is entering low lunar orbit and departing. So, what length and mass? To the rocket equation! A Dragon 2, plus trunk, plus crew, etc, reportedly (?) wet masses about 7385 kg. (In this scenario, the Dragon2 plays the role of the Apollo CSM stack).

Dragon lander is staying in LLO or being discarded. It is playing the role of LM + LOI, where if it is refueled it is just LM because the LOI is replenished.

You need to know the wet mass of the JPAP besides derived Dragon with ascent props and mission payload to surface.

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The math. It takes about 680 m/s to enter low lunar orbit. About the same for the TEI burn. So, 1360MS.

You only need to enter LLO. And, if Dragon was just used as a cargo vehicle to surface, it doesn't even need that, could do a direct landing. If the point was instrument/cargo on the Moon's surface at lowest delta v, one can use the mascons and the cancellation of angular momentum to land at even less delta v budget (very limited number of locations for this).

Now, for a mission planning POV, lets assume we choose an optimum LLO polar access orbit (10km periapsis, 200km apoapsis, longitude 32 degrees) - this is about as low as you'll go, and it will require deft care with small thrusters to maintain such for a month. You could eventually work up to a number of repeat sorties from a single Orion mission, perhaps as many as ten (this would be a logistical challenge requiring multiple "lunar CRS" vehicles/resupply, likely all of them, thus a mission worth doing not EM 1/2). It will cost more to enter this orbit then you've budgeted above - close to 800 m/s given optimal timing. Also, altitude will greatly vary, dropping to 8km and exceeding 200 km as the mascons retard/accelerate the combined SC, not to mention the dispersions either.

Each descent, hover, landing, ascent will require 5 km/sec delta v budget because the sites visited won't be as "easy" as the Apollo ones. So on orbit props will need to support 50 km/sec of props eventually for such a mission.

Which is why the big focus of this thread should be on propulsion and mass reduction. You can also see why you need such an incredible PMF to make a storable propellant single stage reusable lander to work.

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Round up for margins, 1500 m/s. ISP of a SuperDraco is about 240 at sea level. But, the fuel is MMH/NTO, which has a theoretical max of 336, so a superdraco with a vacuum expander bell (with electric actuators for steering) should do a lot better than 240. I'll ballpark it at 275, which I think is conservative.

What I would do is work backwards from the mass flow needed to get the thrust/iSP for the pumps/nozzle, and then you'd deal with the engine/tankage weight as part of the total vehicle's PMF.

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The dry mass of this upper stage should be, using a mass fraction of the S2 (again, I'm being conservative - this service module is just tankage and superdracos, and does not need to support Dragon and Trunk launch loads the way S2 does).

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Annnnd, ack, I can't find a mass figure, even a ballpark, for a superdraco. So, I'm going to totally ballpark it and take a SWAG, so basically my proposed service module for inside the trunk is a scaled down Stage 2 in mass fraction. S2 Dry mass (?) is 3900 kg. I'll scale that down, as the service module is a lot smaller, with fewer structural demands.

FWIW SuperDraco's are 3D printed which means they are very good on mass.

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Dragon2 plus internal SD fuel, etc, has reported mass of 7385kg. I'll add 1000kg for crew plus non-life-support consumables, putting it as 8385kg. That, plus dry service module (I've rounded that up to 1000kg - a very poor mass ratio compared to either F9 stages), 9385kg. So, per the rocket equation, we have a fuel mass for the service module (to get 1500 m/s delta/v) of 7000kg. That's about 1555 gallons. Even assuming the same density as water, it should therefor fit in a cylindrical unit within the trunk.

See above. You don't have delta-v budget to surface and back.

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So, the service module is a cylinder, 1000kg dry mass (It's far smaller than Stage 2, and I'm taking a wild guess as to SuperDraco mass), using 2 Dragon Superdraco engines. Here's where it finally gets relevant to this thread; It's also a baseline lander, derived in part from Dragon 2 components.

Without cargo, by itself, it has a delta/v of 5.5 kps, more than enough to land on the moon and take off again (you need 4.4 kps for that.)

How do you get these numbers?

One usually works from the mission architecture/profile and the desired orbit as a basis.

Then you need to determine LLO entry weight, descent weight at PDI, ascent weight at launch to LLO.

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It can carry 600kg of payload and still do the job (low lunar orbit, land, and come back). Crew accommodations would consist of lightweight aluminum tube Apollo style couches atop the cylinder (They're in space suits - no need for walls, life support, etc.).

Where do you get these numbers? An assumption?

None of these sound right.

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That same lander type, in one-way cargo mode, could land 2500 kg of cargo on the moon - for example a BEAM type module (With a dragon-based life support) for a short term hab, and other supplies. If added capacity is needed on the crew and cargo versions, it could be attained by stretching the tanks;

Nope.

BEAM is an experiment used to increase the TRL of an inflatable module. There is no "off the shelf" surface or orbital hab. Development of such is outside the scope of this thread.

Stretching tanks increases weight nonlinearly. And the assumption here is that you'd use a crasher JPAP with a lightened for ascent, replacement propulsion engines for SuperDraco's on vertical thrust structures (developing new engines alone would exceed the timeline here - SuperDraco's themselves haven't proven themselves, in fact has shortfall on pad abort- Bantam's for Starliner aren't any better).

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it could land and take off with one superdraco even with an additional couple of tons of fuel, due to the low lunar G. (The stretched version could thus include a stowed expandable hab on the crew lander).

Prove this assumption.

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A mission might look like this; a FH launches with a lander plus cargo and a crew lander, either stacked or side by side in a shroud.

Only in a fairing/shroud and on a PAF. The aerostructure is your primary weight reduction target.

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These go to low lunar orbit.

You need an LOI burn.

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A third launch is a fuel depot - not technically hard, as the fuel is storeable hypergolic.

Another vehicle to be developed. How does the fuel get to the vehicle. Where is the crew when the vehicle is fueled?

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4th launch, crew Dragon plus service module.

So no Orion as this thread is written? Does your crew Dragon have all of Orion's capabilities? Can it handle contingencies needed? What if the lander has a shortfall in performance and cannot reach crew vehicle?

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Rendezvous in lunar orbit. Crew handles docking plus topping up the two stages.

What if crew can't transit vehicles? What happens if theres a fueling mishap?

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Cargo lander lands the cargo - if successful, a crew descends on the crew lander, stays a few days, then ascends to rejoin Dragon for a return to Earth.

Is this the fuel vehicle or another?

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Crew lander remains in low lunar orbit, to be refueled from the depot for the next mission. This architecture is flexible; could be used to set up a base, or have a standby emergency ascent vehicle.

Is this a bit far fetched, and relying on a lot of assumptions and guesses? Yup.

Agree.

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I tried to be conservative, but I'm sure I missed some big things. I tried to keep it as cheap as possible, to make it viable for tourism. As part of this, I tried to keep it efficient (such as just couches on the lander, no structure or shell, and no staging, plus possibly reusable.)

To be fair you handwaived.

Sure - try taking the feedback and do some more homework.

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A few huge technical challenges/issues; Can a FH push 16385kg (Dragon plus service module) through TLI? If they can, as claimed, throw 10 tons at mars, maybe, but my guess is probably not. If they do stretch the second stage, then I'd feel better about it being plausible.

Another hard point is Lunar orbital rendezvous; hard to do. Can't use the GPS based system they use for ISS; GPS won't work in lunar orbit.

This part bothers me least.

Many ways to handle this. GPS works poorly in lunar orbit due to geometry (all the sats are all in the same location of the sky, you'd need a couple "orthogonal" to these) and range (delay, noise, and signal strength). One can also do active uplink of positional measurements from precision ground radars)

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The DragonEye laser docking system would - but navigation to close proximity will probably require either crew or a lot of work on the automated navigation system. Further problem, the fuel depot; storable fuel has been transferred in orbit before (such as to ISS) but I have no idea how hard it would be to accomplish for this.

Read my post upthread.

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I'm sure there are major flaws I didn't see - and I'd appreciate criticism and correction.

Hope you make careful use of it.

Many times one gives little here, because no one makes good use of the feedback.

You want more critical feedback, you do the "homework", show your work, and you'll get more involvement.

I'd like to see how the Dragon 2 hatch could be adapted to work with a porch/ladder for EVA egress. And would it be a good idea to have the suits able to join with the hatch or hull as external 'suit locks' after the first EVA? I've become a bit of a fan of suit locks - keeps the dust out of the Lander interior, which was always strongly advocated by John Young and Gene Cernan in particular.

I like these when multiple EVA's are planned or sustained surface ops. Might be different if you are looking at the requirements for a minimum basic lander...